Multifunctional Ti based carbonitride coatings for applications in severe environments

Abstract

In this work, the influence of NbZr and ZrSi addition to TiCN coatings are studied, aiming for their use as protective layers for parts subjected to severe corrosion and wear. The coatings with C/N ratios ranging from 0.4 to 2.5 were deposited using the cathodic arc technique in a mixture of N2 and CH4 gases, on 316 stainless steel discs and Si (111) wafers. All the coatings exhibited residual compressive stresses, with values ranging from approximately-2.4 GPa to −3.5 GPa. The addition of Si led to an increase in hardness, regardless of the C/N ratio. All coatings with high C/N ratio (~2.5) presented slightly lower stress values and superior performance in 3.5% NaCl corrosive solutions, the best performance being obtained for the TiSiZrCN coating, which exhibited the highest protective efficiency to corrosion (97.8%), due to its low corrosion current density (1.734 μA/cm2) and high polarization resistance (31.775 kΩ). The tribological tests, performed at 23 °C and 250 °C, indicated that abrasion and oxidation were the predominant wear mechanism for all coatings. At 23 °C, the friction coefficients of the coated specimens were significantly lower than those of the uncoated samples. When the collective performance across all of the experimental parameters was assessed, the coatings with C/N of about 2.5 proved to be the most suitable candidates to be used in severe service conditions.